package utils;




import java.io.UnsupportedEncodingException;


/**
 * BASE64工具类
 * @author xuyang
 *
 */
public class Base64 {
	private static char[] base64EncodeChars = new char[] {
		'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
		'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
		'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
		'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
		'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
		'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
		'w', 'x', 'y', 'z', '0', '1', '2', '3',
		'4', '5', '6', '7', '8', '9', '+', '/'
	};

	private static byte[] base64DecodeChars = new byte[] {
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
		52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
		-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
		15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
		-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
		41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1
	};

	public static String encode( byte[] data )
	{
		StringBuffer	sb	= new StringBuffer();
		int		len	= data.length;
		int		i	= 0;
		int		b1, b2, b3;
		while ( i < len )
		{
			b1 = data[i++] & 0xff;
			if ( i == len )
			{
				sb.append( base64EncodeChars[b1 >>> 2] );
				sb.append( base64EncodeChars[(b1 & 0x3) << 4] );
				sb.append( "==" );
				break;
			}
			b2 = data[i++] & 0xff;
			if ( i == len )
			{
				sb.append( base64EncodeChars[b1 >>> 2] );
				sb.append( base64EncodeChars[( (b1 & 0x03) << 4) | ( (b2 & 0xf0) >>> 4)] );
				sb.append( base64EncodeChars[(b2 & 0x0f) << 2] );
				sb.append( "=" );
				break;
			}
			b3 = data[i++] & 0xff;
			sb.append( base64EncodeChars[b1 >>> 2] );
			sb.append( base64EncodeChars[( (b1 & 0x03) << 4) | ( (b2 & 0xf0) >>> 4)] );
			sb.append( base64EncodeChars[( (b2 & 0x0f) << 2) | ( (b3 & 0xc0) >>> 6)] );
			sb.append( base64EncodeChars[b3 & 0x3f] );
		}
		return(sb.toString() );
	}


	public static byte[] decode( String str ) throws UnsupportedEncodingException
	{
		StringBuffer sb = new StringBuffer();
		byte[] data = str.getBytes( "US-ASCII" );
		int	len	= data.length;
		int	i	= 0;
		int	b1, b2, b3, b4;
		while ( i < len )
		{
			/* b1 */
			do
			{
				b1 = base64DecodeChars[data[i++]];
			}
			while ( i < len && b1 == -1 );
			if ( b1 == -1 )
				break;
			/* b2 */
			do
			{
				b2 = base64DecodeChars[data[i++]];
			}
			while ( i < len && b2 == -1 );
			if ( b2 == -1 )
				break;
			sb.append( (char) ( (b1 << 2) | ( (b2 & 0x30) >>> 4) ) );
			/* b3 */
			do
			{
				b3 = data[i++];
				if ( b3 == 61 )
					return(sb.toString().getBytes( "ISO-8859-1" ) );
				b3 = base64DecodeChars[b3];
			}
			while ( i < len && b3 == -1 );
			if ( b3 == -1 )
				break;
			sb.append( (char) ( ( (b2 & 0x0f) << 4) | ( (b3 & 0x3c) >>> 2) ) );
			/* b4 */
			do
			{
				b4 = data[i++];
				if ( b4 == 61 )
					return(sb.toString().getBytes( "ISO-8859-1" ) );
				b4 = base64DecodeChars[b4];
			}
			while ( i < len && b4 == -1 );
			if ( b4 == -1 )
				break;
			sb.append( (char) ( ( (b3 & 0x03) << 6) | b4) );
		}
		return(sb.toString().getBytes( "ISO-8859-1" ) );
	}
}